Reliable detection and verification of nuclear materials through both overt and covert means are essential components of global nuclear security. Plutonium, highly enriched uranium, and other radioactive materials are typically identified by their characteristic neutron and gamma-ray radiation. The Department of Homeland Security (DHS) Domestic Nuclear Detection Office (DNDO) is continually searching for technologies that improve radiation detection capabilities and reduce costs.
For many field applications, radiation sensors must be sensitive toward weak signals, simple to operate and interpret, portable and rugged, and sufficiently inexpensive for many-unit purchases. Current technologies for neutron and gamma-ray radiation detection generally only satisfy some of these requirements. For example, gamma-ray detectors based on high-purity geranium (HPGe) exhibit excellent energy resolution, but their sensitivity is insufficient and they must be operated at cryogenic temperatures to achieve optimal performance. For thermal neutron detection, instruments employing helium-3 display high efficiency and good discrimination against concomitant gamma signals, but these sensors are large, require high voltage to operate, are sensitive to vibration, and rely on helium-3, which is experiencing a deepening worldwide shortage. Moreover, none of these technologies are very amenable to covert data collection.